This invention relates generally to ultrasound imaging, and more particularly to visualization of tissue elasticity.
Ultrasound can be used to assess mechanical properties of tissue. In particular, ultrasound can be used for visualization of tissue elasticity, which permits the characterization of tissue.
For visualization of tissue elasticity, a tissue is mechanically deformed and scanned with ultrasound during (or both before and after) deformation. The deformation causes displacement and changes in tissue strain, which are estimated from the acquired ultrasound data and visualized. The visualization process is known in the art as “strain imaging.” An important application of strain imaging is the detection of lesions in tissue, such as tumors.
This imaging technique is established technique that is used primarily on 2D ultrasound data sets of tissues. A 2D data set is acquired, and the tissue is then compressed followed by the acquisition of a second data set. The technique then includes estimating the tissue motion in one or two dimensions from these data sets. The method has been extended to volume ultrasound by imaging a whole volume and determining 3D tissue motion in all three directions. This 3D tissue motion determination is computationally quite intense and takes some time.
A standard technique for breast ultrasound imaging includes obtaining ultrasound image data of a 3D volume displaying a C plane that is perpendicular to the ultrasound transducer used for imaging. A volume is acquired and a slice is taken as the image that is displayed.
In one known method of 2D strain imaging, axial and lateral strains are estimated from 2D ultrasound B mode scans in which the direction of compression is parallel to the axial ultrasound beam direction. Another known technique is to estimate 3D displacement and strain distributions from ultrasound volume data sets. This method also provides estimates of lateral and elevational strain.
However, the estimation of 3D strain distributions is very computationally intensive and thus not practical for real-time imaging. Also, out of plane motion renders conventional 2D strain imaging less accurate than may be desired. A method and apparatus for real-time estimation of strain imaging that is less subject to problems caused by out of plane motion would thus be desirable.